Most of the modern varieties of tropical hibiscus sold today bloom well, although they will cycle in and out of bloom to some extent depending on their growing conditions. For best results, the plant needs full sun all day long, ample water, ample humidity and ample nutrients along with warm temperatures especially at night. In Maryland, these plants are not winter hardy since they are tropical. As a result, they would need to be replaced each year or brought inside each winter. The shorter growing season also naturally means the plants do not bloom as heavily for as long a period as they would in say Florida or the tropics. Sometimes though with a well lit spot indoors and good care they can be induced to bloom as a houseplant as well. As far as which one is "best", personally I find that the single flowered pinks tend to be vigorous and bloom better overall but that is just my opinion and really they are all quite floriferous and wonderful. Your experience (and taste in flowers) might be different.